1. Field of the Invention
This invention pertains to a method and apparatus for assembling a furnace heat exchanger and support plate assembly by forming rigid pressed joints between the burner and flue gas openings in the heat exchanger and cooperating openings in a support plate member.
2. Background
In the manufacture of gas fired hot air furnaces, it is known to fabricate the furnace heat exchangers by forming opposed dish shaped or clamshell sheet metal members which are joined face-to-face to form an enclosure or combustion chamber. Conventional practice in the art of heat exchanger fabrication has been characterized by welding the perimeter seam between the two clamshell sections to form an integral heat exchanger part and by assembling one or more of the heat exchanger parts to additional structure such as a partition plate having openings corresponding to the burner and flue gas openings in the heat exchanger. Welding processes are disadvantageous in that they are expensive, time consuming and create several environmental problems which are hazardous to production personnel and contribute to the overall expense of manufacturing heat exchangers.
One improvement in the art of manufacturing the subject type of heat exchanger is described in U.S. Pat. No. 3,940,837 to John M. Wiese and assigned to the assignee of the present invention. In the Wiese patent, the heat exchanger is formed with a peripheral flange on the opposed clamshell sections which is inserted through an opening in the partition or support plate and is expanded or folded over against the surface of the plate adjacent the opening to secure the heat exchanger to the plate. A layer of insulation material is also preferably inserted between the plate and the heat exchanger flange. Access to the flange for performing the folding operation is convenient, however, one drawback to the arrangement in the Wiese patent pertains to the tendency for the seams formed in the flange at the juncture between the opposed clamshell sections to split or open up during the flange deforming or folding process. This, of course, is detrimental to the structural integrity of the joint formed between the parts and provides a point of leakage of combustion gases from the heat exchanger.
One improved heat exchanger plate joint is disclosed in U.S. patent application Ser. No. 329,778, filed: Dec. 11, 1981 and assigned to the assignee of this invention. The high volume production requirements for heat exchanger and plate assemblies of the type described herein and in the abovementioned application, and the configuration of the openings in the parts themselves, has also led to a need for an improved process and apparatus for assembling a clamshell type heat exchanger to a partition or support plate to form a joint at the respective openings for the burner assembly and flue gas discharge. The requirement to develop a suitable pressed joint heat exchanger and plate assembly has been accentuated by the successful development of the perimeter flange pressed joint disclosed and claimed in U.S. Pat. No. 4,298,061, also assigned to the assignee of this invention.
Moreover, it has been determined that a method and apparatus for providing a suitable no weld connection between a heat exchanger assembly and a supporting plate structure should, in addition to assuring a leakproof joint, be adapted for forming said joint with various thicknesses of metal, or at least being capable of forming the joint while taking into account the tolerances in metal thickness and dimensional variations in mating parts associated with relatively high volume production of heat exchangers for heating equipment for home and industrial furnaces. These objectives have been met with the method and apparatus for manufacturing a heat exchanger and plate assembly in accordance with the present invention.